What do A.M. and P.M. mean?

The expressions A.M. and P.M. indicate ‘before noon’ and ‘after noon’.

The Latin word for ‘midday’ is meridies, from which the word ‘meridian’. So A.M. is an abbreviation for ante meridian, or before midday. P.M is the abbreviation for post meridian, or after midday.

Daylight begins when the Sun rises in the East and ends when it sets in the West. When the Sun is high in the sky, it is exactly between these two positions, half os the day light hours have been spent.

In accident times, the early man could tell the time of day by noticing where the sun stood in the sky. At night he could do so by observing the motion of stars. A Meridian is actually an imaginary line drawn across the sky stretching from the North pole to the South pole. When the Suc crosses the meridian, it is noon. While the Sun is still east of this line or meridian, it is morning. After the Sun crosses this Meridian, it is afternoon.

The world has different time zones. Everyone who loves in the same time zone observes noon at the same moment. In this way, the time differs as we move through each time zone.